Dehydration of alcohols by gasoline extractive distillation



April 1952 w. E. CATTERALL 2,591,672

DEHYDRATION OF ALCOHOLS BY GASOLINE EXTRACTIVE DISTILLATION v Q T I F l)(D A H QT 1.5g

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T m o (Jillian: E.Cattera-ZZ {Inventor bgwdbborneg April 8, 1952 w. E.CATTERALL 2,591,672

DEHYDRATION OF ALCOHOL-S BY GASOLINE EXTRACTIVE DISTILLATION Filed Jan.3, 1949 2 SHEETS--SHEET 2 GASOLINE FEED 2 9 WATER ALcoHoL FEED i coHoLGAsoLmE T E LEND SOLVENT QEcvcL N L OJ tllzjam E. (fatter-all Invento bMM aLLorEEg- Patented Apr. 8, 1952 DEHYDRATION F ALCOHOLS BY GASOLINEEXTRAGTIVE DISTILLATION William E. Catterall, Elizabeth, N. .L, assignorto Standard Oil Development Company, a corporation of DelawareApplication January 3, 1949, Serial No. 68,876

4 Claims. 1

This invention relates to the dehydration of alcohol or mixturescontaining alcohol by means of extractive distillation employinggasoline as the extractive distillation solvent. The invention is alsoconcerned with the production of gasoline-alcohol blends by a processwherein the alcohol is dehydrated by means of extractive distillationusing as the solvent all, or a fraction of the gasoline into which it isdesired to blend the alcohol.

It is an object of this invention to dehydrate neutral organicoxygenated compounds such as alcohols, kctones, ethers, or mixturesthereof. It is an object of this invention to dehydrate neutral organicoxygenated compounds such as alcohols, ketones, ethers, or mixturesthereof in such a manner that the dehydrated compounds becomesimultaneously blended in gasoline.

It is a further object of this invention to prepare a gasoline blendcontaining alcohols,

ketones, ethers, etc., or mixtures thereof. It .is-

also an object of this invention tofully and economically utilize theprocess streams resulting from a hydrocarbon synthesis operation.

Various processes are known to the art in which a mixture ofhydrocarbons and organic oxygen containing compounds are produced. Someof these processes are: the low temperature carbonization of coal, peatand similar materials; destructive hydrogenation of coals, wood andshales; the methanol synthesis; the so-called oxo synthesis in whicholefins are reacted in the presence of carbon monoxide and hydrogen; thenumerous oxidation processes, particularly the oxidation of propane andother petroleum fractions; and the well-known hydrocarbon syn-- thesisoperation. The products of the abovementioned reactions are usuallynumerous, but can be classified into two groups, namely, thehydrocarbons and the non-hydrocarbons, the latter including the alcoholsand other oxygenated compounds.

It is well known that alcohols, ketones, ethers, etc., may be blendedwith gasoline and a suitable motor fuel thereby produced. Alcohols suchas ethanol, isopropanol, n-propanol, etc., are usually obtained,particularly from the synthesis reactions mentioned above, as aqueousazeotropic mixtures which must be dehydrated before the alcohol can beblended with gasoline. This dehydration is normally carried out byazeotropic distillation using an entraining agentv such as ethyl ether,isopropyl ether, benzene, cyclohexane, etc. Such dehydration processesinvolve considerable cost and are uneconomlcal from a heat consumptionstandpoint. The pur pose of this invention is to provide an improvedprocess for .efiecting the dehydration and at the same time recovering ablended gasoline from the dehydration operation.

According to the terms of this invention the dehydration of the alcoholor other oxygenated compounds employed in the gasoline blendingoperation is carried out by means of extractive distillation using asthe solvent all or a fraction of the gasoline into which it is desiredto blend the alcohol or other material. The process is particularlyapplicable in the hydrocarbon synthesis operation wherein the productsseparate into a hydrocarbon layer including gasoline and a water layerincluding alcohols, ketones, etc. In the overall process of recovery ofsynthesis products, the water layer is subjected to water extractivedistillation to reject light materials such as acetaldehyde,propionaldehyde, ethyl acetate, and some acetone, followed byconcentration of the remaining water layer by straight fractionation toreject the acids and the bulk of the water. The water layer which is nowreduced toa concentrated alcohol-ketone mixture is then dehydrated bymeans of extractive distillation usingessentially all or part oftheproduct gasoline stream from the synthesis plant as the solvent. In atypical synthesis plant based on natural gas, the final gasoline mixturewould contain about 10 volume per cent oxygenated compounds.

Figure 1 represents a simplified flow plan of a typical process whichdescribes one modification of the present invention. Referring to Figure1, the numeral 1 represents a synthesis zone in which a mixture ofhydrogen and carbon oxides is reacted in the presence of a catalyst suchas sintered red iron oxide promoted with potassium carbonate. In thesynthesis zone the reaction takes place'at atemperature of about 300 F.to 800 preferably at about 650 F., and at pressures in the range of 25to 750 p. s. i., preferably about 400' p. s. i. The gaseous eiiluentleaves the synthesis zone via line 2, and is passed to a condenser andscrubber notshown, after which it enters separator 3. In separator 3',the condensed product separates into two phases, namely, an upperhydrocarbon phase 6,. and a lower water phase 4. The hydrocarbon phaseis led via line 6 to fractionatorl, where there is taken overhead vialine 8, material of the C4 and lighter range, while hydrocarbons inrange of C5 and above are removed as bottoms via line 9 and introducedto treater it. Inthe treater It,

the hydrocarbons are treated in the vapor phase with bauxite or othercracking catalyst at a temperature of approximately 700 to 900 F. In thetreater the mixture undergoes a mild. cracking during which anyoxygenated compounds present are decomposed to hydrocarbons. Thehydrocarbons also undergo isomerization and cracking which improve thequality of the material. The total vapor eiliuent is passed from thetreater l via line H to fractionator 12. In fractionator 12, thehydrocarbons are separated into an overhead comprising C3 and lighterhydrocarbons, a gasoline side stream comprising the C4. and heaviermaterials boiling up to 430 F., and a bottoms boiling at 430 F. andabove, which is removed via line I5. The light hydrocarbons emergingfrom fractionator I and I2 via lines 3 and I3 respectively, are passedto a polymerization zone wherein the olefins are polymerized to polymergasoline by a typical polymerization process such as that carried out inthe presence of the well-known UOP polymerization catalyst at atemperature of 300 to 500 F., and at a pressure of 250 to 2000 p. s. i.The resulting gasoline recovered from the polymerization is known aspolymer gasoline.

Returning to the drawing, the water layer 4 is withdrawn from separator3 via line It and introduced into extractive distillation column 18. Inthis column, the water layer is distilled countercurrent to internalliquid water reflux, which is introduced into the column .via line is.The water is introduced in amounts sufficient to insure the distillationof light neutral nonalcoholic oxygenated compounds from the water layer.To this extent, water in the amount above 50 mol per cent, preferably'10 to 80 mol per cent, is maintained in the liquid on the bulk or theplates in the extractive distillation tower. Sullicient water is addedthrough line l9 to insure such water concentration. The distillateremoved overhead via line consists of low boiling or water-insolublematerials such as acetaldehyde, propionaldehyde, ethyl acetate, methylacetate, dimethyl acetal, some acetone, etc. The vapors are condensed incondenser 2| and removed from the system via line 22, however, part ofthe condensate is refluxed to column I8 via line 23. The bottoms fromcolumn l8, which now comprise an aqueous solution of the alcohols,acids, and higher molecular weight oxygenated compounds of other types,is removed via line 24 and introduced into concentrating column 25. Thiscolumn is so operated as to remove overhead the alcohols and otherneutral oxygenated compounds via line 26. The distillate is condensed incondenser 21, and removed via line 23 as feed to the dehydration column32 as will be explained below. Part of the condensate is returned asreflux to column via line 29. Bottoms from the concentrating columncomprise an aqueous solution of acids present in the original waterlayer, and these are removed to storage via line 30. However, a portionof the aqueous bottoms may be employed as the extractive distillationsolvent entering through line l9. Open steam may be supplied to thebottoms of column l8 and 25 or reboilers may be provided.

This water extractive distillation method of eliminating compoundsunsuitable for gasoline addition is only an example used for purposes ofillustration. Other processing methods such as ordinary fractionaldistillation may be suitable for particular mixtures and will beapparent to those skilled in the art.

Referring now to the dehydration column 32, there is introduced theretovia line 28, an aqueous mixture of the alcohols originally present inthe water layer together with any higher molecular weight neutraloxygenated compounds such as lretones, ethers, etc. Gasoline orfractions of gasoline are introduced into the dehydration column at apoint near the top thereof via line33 Heat is supplied indirectly inreboiler 43. The dehydration column is operated in such a manner thatthe water present in the alcohol feed is removed overhead from thecolumn. Sufficient gasoline is added to the top of the tower to permitwithdrawing the gasoline from the bottom of the tower with thedehydrated alcohol. The necesary condition which must be met in theliquid mixture on substantially all the plates of the tower is that thewater must be more volatile than the bulk of the solvent (as well asbeing*-.

more volatile than the alcohol) otherwise water will be withdrawn fromthe bottom of the tower with the solvent and alcohol. Complete removalof the Water will generally be assured by maintaining a minimum gasolineconcentration in the liquid on the plates of the tower of at least 40molper cent, for example, 40 mol per cent to 99 mol per cent, preferablyabove '70 mol per cent. Such concentrations permit the completevaporization of the water and accomplish the withdrawal from the bottomof the tower of substantially anhydrous alcohols dissolved in theextractive solvent.

The hydrocarbon solvent added to the top of the tower and descending asreflux has very limited capacity to absorb either water or lighteralcohol such as ethanol from the ascending vapor, and therefore to avoidexcessive carryover of alcohol into the overhead, the amount of vaporascending the tower should be held close to minimum necessary to assurecomplete reinoval'of water from the bottoms. For the same reason, thehydrocarbon concentration usually remains high, for example, 96 to 99mol per cent, above the feed. At the feed point, the feed mixes with thesolvent and substantially decreases the hydrocarbon concentration in thereflux. It is the hydrocarbon concentration in the section of the towerbelow the feed point that is critical to the separation of water fromalcohol, and it is in this zone that a hydrocarbon concentration of atleast 40 mol percent, preferably above 70 mol per cent, must bemaintained to assure a favorable relative volatility of water toalcohol.

It is to be understood that during the gasoline extractive distillation,some of the gasoline passes overhead via line 34 together with thewater. The total overhead is condensed in condenser 35 and led toseparator 36 wherein the condensate separates into an upper gasolinelayer 37 and a lower water layer 38 which is removed from the system vialine M. The gasoline layer may be refluxed to the column via line 39, orremoved entirely or in part via line 40 with the blended gasolineleaving the column as bottoms via line 42. Part of the alcohol or otheroxygenated compounds in the feed may also pass overhead. To recover theportion of such material which dissolves in the decanted water layer,this water may be recycled to column 25 via line 24 or other feed point.

The gasoline fraction obtained from fractionator i2 is an excellentsource of solvent for the dehydration process and to this endthefraction may be removed via line H and led to column 32 where itenters via line 33. Polymer gasoline eral, a gasoline boiling in therange of 100 F. to 430 F., preferably 150 F. to 430 F. is suitable.

It is desirable that the vapor pressure of the gasoline used be'as lowas possible to avoid the necessity of vaporizing excessive quantities ofgasoline in the. distillation, which causes excessive heat consumption.Therefore, it is desirable to use a gasoline stock which does not yethave light ends such as C4 hydrocarbons blended in for vapor pressurerequirements. Excessive light ends also serve to increase the amount ofgasoline which must be withdrawn as overhead product to avoid thebuild-up of light ends in the upper section of the column. Thiswithdrawal of hydrocarbon from the overhead decreases the net solventdownflow in the tower, and therefore decreases the solvent concentrationand decreases the efiective. relative volatility of water to alcohol.

A relatively pure hydrocarbon such as diisobutylene, benzene or toluenemight be used as the solvent, or a commercial mixture of aromatics suchas motor benzol would be suitable. There will be some differences in theefiectiveness of the solvent depending on whether the hydrocarbon ispredominantly paraifin, olefin, naphthene, or aromatic, but allhydrocarbon types are suitable. If a pure hydrocarbon or narrow-boilingfraction is used as the solvent, the boiling range should be above about30 0., preferably above about 60 C., to avoid excessive solvent flowrequirements and excessive heat requirements.

Although the invention has been described in regard to the dehydrationof alcohols, the process isv equally applicable to the dehydration ofmixtures of alcohols or to mixtures of alcohols with other neutraloxygenated compounds such as ketones, ethers, etc. The presence of anyoxygenated compound suitable for blending into gasoline may be toleratedin the feed to the dehydration process. The invention is mostadvantaeously applied to the dehydration of individual or mixed C2 andC3 alcohols which form homogeneous water azeotropes, and thus cannot bereadily dehydrated by straight distillation. The invention is alsoapplicable to an alcohol mixture containing lower and higher boilingalcohols than those mentioned, although a large fraction of any methanolpresent would distill overhead due to its high vapor pressure andlimited solubility in hydrocarbons. The process is particularly suitableto aqueous alcohol mixtures derived from the oxidation of lighthydrocarbons Or from the hydrocarbon synthesis involving hydrogen andcarbon monoxide. To produce a stable non-corrosive gasoline, it isnecessary to remove the bulk of such non-alcoholic contaminants asacids, esters, and aldehydes. This removal is assured by the waterextractive distillation step already outlined.

During the water extractive distillation operation as carried out incolumn [8, considerable amounts of acetone and methanol may remain inthe bottoms removed from the water extractive distillation column. Thesevolatile compounds would likewise concentrate in the overhead taken fromthe concentrating column and therefore would be present in the feedentering the dehydration column via line 28'. These materials woulddistill overhead to a large degree in the dehydration column and wouldthen tend to accumulate in the dehydrating tower overhead stream if thedecanted Water is recycled to column 25. This accumulation may not bedisadvantageous unless it seriously interferes with phase separation. inthe decanter. However, to prevent the concentration of large amounts ofacetone and methanol in the dehydration column, it may be necessary toremove these components from the. system, for example, as an anhydrousstream from the top of concentrating column 25. In t is event, theremaining neutral-oxy compounds, including the alcohols, etc., would beremoved as a side stream and then fed to the dehydration. column 32.Other methods of removing these components will be apparent to those.skilled in the art.

It has been ascertained that the concentration of the gasoline solventhas a definite efiect on the relative volatility (alpha) of Water to thealcohol being.v dehydrated. For example, the relative volatility ofwater to ethanol in 70 to mol per cent hexane solution was estimated tobe within the range of 3 to 5. The steam requirement when operating withhexane under optimum conditions is estimated to be 6 to 10 lbs. perpound of water removed, which is very favorable compared to the 20 to 40lbs. of steam required in conventional azeotropic distillation practice.The extractive distillation process has this strong advantage overazeotropic distillation because a much higher solvent concentration canbe maintained below the tower feed point and a much better relativevolatility in this critical region can be realized. In either case thesolvent concentration is very high above the feed point and the relativevolatility of water to alcohol is very high in this zone; however, thecapacity of the solvent to reflux ethanol is limited, and it may requirean undue solvent addition to avoid the presence of some ethanol in theoverhead.

This process is particularly suitable for use when it is desired toproduce an alcohol-gasoline blend or blending stock from the alcohol tobe dehydrated. When the dehydrated alcohol in pure form is the desiredproduct, it would be necessary to separate the alcohol from thehydrocarbon-alcohol mixture obtained from the bottom of the extractivedistillation tower, and additional processing equipment would berequired. This method would be considerably more expensive than theusual azeotropic dehydration method.

Under certain circumstances it may be desirable to use as the extractivedistillation solvent a greater quantity of hydrocarbon than the alceholis to be blended with. In this case by separate distillation of thebottoms mixture a portion of the gasoline may be recovered alcohol-freefor recycling to the top of the extractive column. These twodistillation operations can be combined in one tower to eilect animportant heat economy as shown in Figure 2.

Referring to Figure 2 aqueous alcohol feed is introduced into tower Ivia line 2 at a point above the midsection of the tower while gasolineis introduced via line 3 at the top of the tower. The alcohol-gasolineblend is withdrawn as a liquid sidestream from the lower section of thetower via line 4 instead of from the bottom of the tower- Overheadvapors are removed via lin 5, condensed in condenser 6 and separated indecanter 1 into a gasoline phase which is refluxed to the tower via line8 and an aqueous phase which is removed via line 9. Additionalhydrocarbon iord'ecycle is withdrawn from the bottom via line I andreturned to the gasoline feed line 3. The vapor supplied to the bottomof the tower via line 12 from the reboiler H serves both to stripalcohol from the hydrocarbon recycle in the lowest zone of the tower andto accomplish the extractive distillation in the higher zones.

Without attempting to explain the mechanism by which the desiredseparation of water occurs in the dehydration column, it can be saidthat the process is one of vapor-liquid extraction in which the vaporscontain a greater concentration of water relative to the alcohol beingdehydrated than under the normal fractional distillation conditions inthe absence of the considerable amount of liquid gasoline internalreflux; It is evident from the results obtained'that the gasolineemployed within the limits specified increase the effective vaporpressure of water in comparison with the vapor pressure of the alcoholbeing. dehydrated, thus allowing the water to pass overhead from thedistillation zone. The temperature of the aqueous alcohol fed to thedehydration column is preferably close to the temperature of the liquidon the plate at the point of addition'of the feed, although it may belower to partially condense vapors ascending to the feed plate. Forcontinuous efficient operation the gasoline must be added continuouslynear the top of the column while the aqueous alcohol being' purified iscontinuously fed to the column at a lower point, and while suflicientheat is provided to afford di tillation throughout the column. The feedstream 1 may be preheated to a temperature close to that of the internalliquid gasoline reflux under equlibrium reboiling conditions at thepoint of introduction. The preheated aqueous feed may be liquid,partially vaporized, or completely vaporized when introduced into theextractive distillation column. Vapors of water and of the alcohol beingdehydrated pass upwardly through the distillation zone in contact withdescending internal liquid gasoline reflux under equilibrium reboilingand refluxing conditions.

The quantity of gasoline required to be introduced continuously at thetop of the distillation sections of the tower under certain c-onditions,but no serious disadvantage *results from this situation if properreflux flow down the tower can be maintained.

The gasoline employed as the extractive distillation solvent may be thegasoline produced in the hydrocarbon synthesis operation, the polymergasoline recovered from the polymerization.

process described, benzene, motor benzol, or any gasoline or gasolinefraction produced extraneously, as for example, by catalytic cracking,thermal cracking, alkyiation, etc.

The dehydration tower may be operated at atmospheric pressure, undervacuum, or at superatmospheric pressures.

The invention is illustrated by the examples set out in the table. Thetable shows the results of experiments conducted in an extractivedistillation column of 30 plates. In the experiments the aqueous alcoholwas fed to the 15th plate and. the extractive distillation solvent tothe th plate. The total vapor taken overhead Was condensed and twolayers formed which were decanted. The hydrocarbon phase was refluxed,if desired, to the column while the aqueous phase was removed from thesystem. The hydrocarbon when employed as reflux was preheated prior toits return to the column. In the runs described benzene was employed inapproximately 80 mol per cent concentration in the liquid reflux belowthe point of addition of the solvent and the catalytically-crackednaphtha in approximately 90 mol per cent concentration.

-- The alcohol feed was a blend bearing the following analysis:

A. ,On a wet basis zone for accomplishing the desired dehydration isVolume considerably greater than the quantity of conper cent densatewith which it becomes homogeneously Alcohols 83.5 mixed on each plate inorder to make the gaso Water 16.5 line concentration of the internalreflux substan- B. On an anhydrous basistially above a critical minimumin the range Ethanol 55.0 above 40 mol per cent. With adequategasoline5s n-Propanol 32.0 concentration in the internal reflux for effectingn-Butanol 10.0 the dehydration, the alcohol being dehydrated is n-Amylalcohol 3.0

TABLE Dehydration of aqueous alcohols by hydrocarbon extractivedistillation OPERATING CONDITIONS Alcohol Feed Solvent Feed Hydm Temp.C. 0!

a bon Run lle flux Composition Material ccJln. fgga %!Z;

r10 .l C1-C5 Alcohol rs Benzene (so 510 180 65 Blend. mol per cent). 125C2C5 Alcohol 69 Catcracked 940 0 67 56 Blend. Naphtha mol per cent).

1 Boiling range 47 C.198 O.

RESULTS Overhead Product Bottoms Product Per Cent Run Hydrocarbon PhaseAqueous Phase if fzgg fi Vol. For Weight A news P o t P c t m/hr' A1 i li (gent Olgerhead or on er en co 0s a or (gm/hr Alcohols Alcohols 120 033 24 510 1 0.1 7.2 l25 365 ll 30 67 575 2 75 0. 1 35 What is claimedis:

1. A method of simultaneously dehydrating "aqueous alcohols to afractional distillation zone at an intermediate point thereof,continuously adding hydrocarbon boiling in the gasoline boiling range of100 F. to 430 F. as solvent to the fractional distillation zone at apoint substantially above the aqueous alcohols feed point to maintain aninternal liquid reflux having a gasoline hydrocarbon content in therange above 70 mol per cent below the point of addition of the gasolinehydrocarbon, distilling from said aqueous alcohols a vaporous mixturecomprising water wherein the distilled vaporous mixture flowscountercurrent to the gasoline hydrocarbon reflux, withdrawing adehydrated mixture of gasoline and C2 to C5 alcohols as a lowersidestream from the fractional distillation zone, and withdrawinggasoline hydrocarbon substantially free of water and alcohols as bottomsfrom the fractional distillation zone.

2. The method of claim 1 in which the gasoline hydrocarbon substantiallyfree of water and a1- cohols is recycled as solvent to the fractionaldistillation zone.

3. A method of simultaneously dehydrating a mixture of aqueous alcoholscontaining 2 to 5 carbon atoms per molecule and preparing analcohol-gasoline blend therefrom which comprises continuously feedingthe aqueous alcohols to a fractional distillation zone at anintermediate point thereof, continuously adding hydrocarbon boiling inthe gasoline boiling range of 100 F. to 430 F. to the fractionaldistillation zone at a point substantially above the aqueous alcoholfeed point to maintain an internal liquid reflux having a content ofsaid hydrocarbon in the range above 70 mol per cent below the point ofaddition of the gasoline hydrocarbon, distilling from said aqueousalcohols a vaporous mixture comprising substantially all the waterpresent in the aqueous alcohols wherein the distilled vaporous mixtureflows countercurrent to the gasoline hydrocarbon reflux and withdrawinga dehydrated solution of alcohols containing 2 to 5 carbon atoms in saidgasoline hydrocarbon from a lower portion of the fractional distillationzone.

4. A process for recovering a blend of gasoline with alcohols andketones from the reaction product obtained in the hydrogenation ofcarbon monoxide, said product containing hydrocarbons, acids, andneutral oxygenated compounds comprising aldehydes, ketones, alcohols,and esters which comprises separating the product into an oil phase anda water phase wherein each phase contains at least a portion of saidhydrocarbons, acids and neutral oxygenated compounds, distilling thewater phase in a water extractive distillation zone wherein thedistilled vapors ascend countercurrent to an internal liquid refluxhaving a water content above mol per cent, removing as a distillate fromthe water extractive distillation zone a mixture containing hydrocarbonsand neutral non-alcoholic oxygenated compounds including aldehydes,esters and a portion of the ketones, removing as bottoms from the waterextractive distillation zone an aqueous acid solution of alcohols andthe remainder of the ketones, stripping an aqueous solution of alcoholsand the ketones from the aqueous acid solution, separating a gasolinefraction boiling in the range of F. to 430 F. from said oil phase,distilling the aqueous solution of alcohols and ketones in a secondextractive distillation zone wherein the distilled vapors ascendcountercurrent to an internal liquid reflux having a content of saidgasoline, above 70 mol per cent, removing as distillate from said secondextractive distillation zone a mixture comprising essentially all thewater, and recovering as bottoms from the second distillation zone ablend of said gasoline and said alcohols and ketones substantially freeof water.

WILLIAM E. CATTERALL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,412,233 Ellis Apr. 11, 19221,420,006 Whitaker June 20, 1923 1,474,983 Schreiber Nov. 20, 19232,012,199 McElroy Aug. 20, 1935 2,290,636 Deanesly July 21, 19422,339,160 Dunn et al Jan. 11, 1944 2,371,010 Wolfner Mar. 6, 19452,379,110 Souders June 26, 1945 2,426,705 Patterson et al Sept. 2, 19472,467,966 Clark Apr. 19, 1949 2,470,782 McGrath et al. May 24, 19492,472,219 Lyons June 7, 1949

1. A METHOF OF SIMULTANEOUS DEHYDRATING AQUEOUS ALCOHOLS CONTAINING 2 TO5 CARBON ATOMS AND PREPARING AN ALCOHOL-GASOLINE BLEND THEREFROM WHICHCOMPRISES CONTINUOUSLY FEEDING THE AQUEOUS ALCOHOLS TO A FRACTIONALDISTILLATION ZONE AT AN INTERMEDIATE POINT THEREOF, CONTINUOUSLY ADDINGHYDROCARBON BOILING IN THE GASOLINE BOILING RANGE OF 100* F. TO 430* F.AS SOLVENT TO THE FRACTIONAL DISTILLATION ZONE AT A POINT SUBSTANTIALLYABOVE THE AQUEOUS ALCOHOLS FEED POINT TO MAINTAIN AN INTERNAL LIQUIDREFLUX HAVING A GASOLINE HYDROCARBON CONTENT IN THE RANGE ABOVE 70 MOLEPER CENT BELOW THE POINT OF ADDITION OFTHE GASOLINE HYDROCARBON,DISTILLING FROM SAID AQUEOUS ALCOHOLS A VAPOROUS MIXTURE COMPRISINGWATER WHEREIN THE DISTILLED VAPOROUS MIXTURE FLOWS COUNTERCURRENT TO THEGASOLINE HYDROCARBON REFLUX, WITHDRAWINING A DEHYDRATED MIXTURE OF AGASOLINE AND C2 TO C5 ALCOHOLS AS A LOWER SIDESTREAM FROM THE FRACTIONALDISTILLATION ZONE, AND WITHDRAWING GASOLINE HYDROCARBON SUBSTANTIALLYFREE OF WATER AND ALCOHOLS AS BOTTOMS FROM THE FRACTIONAL DISTILLATIONZONE.